LXF 156 makes heavy weather of finding a case for the Raspberry Pi : folding out of projector transparency, Lego blocks .... I don't think I would want those as a permanent fixture in the living room

Building electronics is a hobby of mine. I have made some cases myself from sheet steel when I was fussy about the size, but the simplest way is to buy a ready made box from somewhere like Maplin. Last time I looked they had quite a wide selection that would make the job look professional.